The ultimate goal of this proposal is to understand the contribution of Vstat120 expressing oncolytic viruses on OV propagation, tumor biology and anti-tumor efficacy. These results will lead to a better understanding of OV therapy induced changes in tumor biology and will lead to the development of a dually armed cancer killing OV. The OV treatment of tumors relies on cancer-specific replication of the virus leading to tumor destruction with minimal toxicity to adjacent non-neoplastic tissue. Results from six clinical trials using replication competent OVs to treat patients with malignant glioma have shown the new modality to be relatively safe, but high expectations of efficacy remain unmet (1, 2). The tumor's microenvironment is increasingly recognized as an important determinant for its progression and its response to therapeutics. My laboratory has recently created two oncolytic viruses, armed with an anti-angiogenic gene. We now propose to elucidate the role of this angiostatic protein in viral propagation, glioma biology and OV efficacy.